32 ATTAINMENT OF VERY LOW TEMPERATURES. 



a gasometer of the type I have described, there is a considerable 

 advantage in one of the kind shown in fig. 1 1 , B. Such a gasometer is 

 in use in connection with the Hquefaction plant which I designed for 

 Professor Auschiitz of Bonn. Gasometers of this type are used for the 

 storage of acetylene. 



XIV. Conclusion of Part I. 



I have so far succeeded in designing an apparatus by means of 

 which I can at a comparatively small cost produce quantities of liquid 

 hydrogen sufiicient for experimental purposes. I have usually ob- 

 tained half a liter as a maximum quantity, as it has always been 

 sufficient for the experiments I have had in hand. 



I am at present engaged in designing an apparatus in which the 

 liquid hydrogen will be produced inside a metal chamber, and will be 

 drawn off through a cock. The elimination of the glass vacuum 

 vessel presents obvious advantages. At the same time I am investi- 

 gating the conditions most favorable to effective heat interchange in 

 the regenerator coil D, figs. 4, 6, of the apparatus. The dimensions 

 of the coils (p. 16) in the machines I have already experimented with 

 has always been one quarter of the size of the coil of the Hampson air 

 liquefier, the temperature gradient being in one case 50° and in the 

 other 200°. The results of my experiments appear to indicate that 

 these dimensions are too small, for the reason that the heat interchange 

 is a function not only of the conductivity of the metal of which the 

 coils are constructed, but also of certain properties of the gas. Fur- 

 ther, it appears probable that the spacing of the coils will have a con- 

 siderable influence on the efficiency of the apparatus, and that for 

 hydrogen, which has a low viscosity, the coils should be closer together 

 than in a machine which is designed to liquefy air. 



In conclusion I wish to express my indebtedness to the Smithsonian 

 Institution for the assistance it has given me in carrying out these 

 investigations. 



